CNN contributors Van Jones and Jeffrey Lord had a heated moment in March 2016 during the channel's Super Tuesday coverage – and it was one of the most compelling TV moments of the 2016 race. (Peter Stevenson/The Washington Post)

It was earnest, substantive, respectful and important. It was the best five minutes of television in the presidential campaign.

After Lord defended Trump, Jones, a progressive activist, interjected, and the two engaged in a long (by live TV standards) and heated discussion. Here's part of their exchange:

LORD: Let's talk about what [Trump] said about the Klan. Here's a guy who disavowed this many, many, many times. You hear this statement from Mitt Romney and Paul Ryan today. I like Paul Ryan. We both worked for Jack Kemp. Jack Kemp would be appalled at this. I hate to say this about the Republican establishment but their view of civil rights is to tip the black waiter five bucks at the country club. This is atrocious. This is atrocious. This is why Donald Trump has the ability — because he's not going to patronize people.

JONES: Well, hold on a second. First of all, there's a lot of things you said that I could take you on about. But I want to be very, very clear. The things that Donald Trump has done — and not just in this race — are horribly offensive. You can go back with this guy for a long time. I want to talk. I want to talk. Because this is important.

LORD: I didn't say anything yet.

JONES: You breathed. You can go back to the central jogger case where he came out and had innocent black kids winding up in prison.

LORD: No, innocent kids.

JONES: Hold on a sec — innocent black kids. Listen, hold on a second. We have a big problem at this point now. Because I agree with you about a lot. I think we have taken him not seriously, we have not respected his voters, but there is a dark underside here, and S.E. is right. He is whipping up and tapping into and pushing buttons that are very, very frightening to me and frightening to a lot of people. Number one, when he is playing funny with the Klan, that is not cool.

LORD: He didn't play funny with the Klan.

JONES: Hold on a second. I know this man when he gets passionate about terrorism. I know how he talks about terrorism. The Klan is a terrorist organization that has killed ...

LORD: A leftist terrorist organization.

JONES: You can put whatever label you want; that's your game to play.

LORD: No, it's important to history.

JONES: We're not going to play that game.

LORD: We're going to understand history.

JONES: No, you need to take a serious look at the fact that this man has been playing fast and loose and footsie — when you talk about terrorism, he gets passionate. He says, "No, this is wrong." But when you talk about the Klan, oh, I don't know, I don't know. That's wrong. And then you came on the air and you said, well this is just like when Rev. Wright was speaking. Rev. Wright never lynched anybody, Rev. Wright never killed anybody.

LORD: Rev. Wright is an anti-Semite.

JONES: Rev. Wright never put anybody on a post. And you guys play these word games, and it's wrong to do in America.

Wright, for those who might have forgotten, is President Obama's former pastor who became a lightning rod during the 2008 election, as video clips of his fiery sermons — which often centered on racial inequality and America's shortcomings on that front — circulated online.

There was more between Jones and Lord, and the transcript doesn't do it justice. Did I mention you need to watch this?

Equally striking as the passion with which Jones and Lord disagreed was the civility with which they did. They never descended into the kind of personal insults that have marred the campaign. What made the moment so compelling was the unmistakable sense that each man was trying to persuade the other because he cared about his counterpart and valued his opinion.

It was the difference between a bar fight and an argument over Thanksgiving dinner. Drunken combatants just want to beat each other up, but relatives desperately want to win converts to their way of thinking.

Just look at the way Jones used his hands; for much of the discussion, he gestured emphatically with his left while resting his right calmly on Lord's shoulder. The former made his point; the latter said, "Come here. I really want you to understand my perspective because what you think matters to me."

When anchor Anderson Cooper finally took back control of the telecast — after wisely stepping back to let Jones and Lord have their debate — he suggested their passion might foreshadow the general election. That's probably too optimistic. Trump and Hillary Clinton won't be trying to change each other's minds.